Globally, the Indian Ocean appears to have the greatest blue whale (Balaenoptera musculus ssp) acoustic diversity, with at least four acoustic populations from three defined sub-species. To understand how these different populations use this region as habitat, we first need to characterize their spatial and seasonal distributions. Here, we build on previous passive acoustic monitoring studies and analyze a passive acoustic dataset spanning large temporal (9 years) and spatial (3–9 sites covering more than 12 million km² of potential acoustic habitat in the southwest Indian Ocean) scales. A novel detection algorithm was employed to investigate the long-term presence of Antarctic blue whale and SEIO and SWIO pygmy blue whale calls. We found that Antarctic and pygmy blue whales have completely different spatial and seasonal distribution in the southern Indian Ocean. Antarctic blue whales are heard almost year-round on the whole array, with great inter-annual variability. The two pygmy blue whales share a highly stable seasonal acoustic presence, but their geographical distributions overlap at only a few central Indian Ocean sites. However, Antarctic and pygmy blue whale acoustic co-occurrence is common, especially in sub-tropical waters. These temporal and spatial distributions strengthen our understanding of seasonal occurrence and habitat use of distinct populations of blue whales in the southern Indian Ocean. A better comprehension of the ecology of Indian Ocean blue whales will require interdisciplinary studies to examine the drivers of the variability seen from passive acoustic studies.

在全球范围内，印度洋似乎具有最大的蓝鲸（Balaenoptera musculus ssp）声多样性，至少有来自三个已定义亚种的四个声种群。为了了解这些不同的人口如何利用该地区作为栖息地，我们首先需要表征其空间和季节分布。在此，我们以先前的被动声监测研究为基础，并分析了跨越大的时间（9年）和空间（3–9个站点，覆盖超过1200万公里²）的被动声数据集印度洋西南部潜在的声学栖息地的规模）。一种新颖的检测算法被用来调查南极蓝鲸和SEIO和SWIO侏儒蓝鲸的长期存在。我们发现，南印度洋和南极侏儒蓝鲸在空间和季节分布上完全不同。在整个阵列中，几乎全年都会听到南极蓝鲸，且年际变化很大。两只侏儒蓝鲸有着高度稳定的季节性声学存在，但它们的地理分布仅在印度洋中部几个站点重叠。然而，南极和侏儒蓝鲸的声音共存是常见的，特别是在亚热带水域。这些时空分布加强了我们对印度洋南部不同蓝鲸种群的季节性发生和栖息地利用的理解。要更好地了解印度洋蓝鲸的生态状况，就需要进行跨学科研究，以研究从被动声学研究中看到的变异性的驱动因素。